A Novel Inhibitor of Poly(ADP-Ribose) Polymerase-1 Inhibits Proliferation of a BRCA-Deficient Breast Cancer Cell Line via the DNA Damage-Activated cGAS-STING Pathway.

Loss-of-function mutations in the Breast Cancer Susceptibility Gene (BRCA1 and BRCA2) are often detected in patients with breast cancer. Poly(ADP-ribose) polymerase-1 (PARP1) plays a key role in the repair of DNA strand breaks, and PARP inhibitors have been shown to induce highly selective killing of BRCA1/2-deficient tumor cells, a mechanism termed synthetic lethality. In our previous study, a novel PARP1 inhibitor─(E)-2-(2,3-dibromo-4,5-dimethoxybenzylidene)-N-(4-fluorophenyl) hydrazine-1-carbothioamide (4F-DDC)─was synthesized, which significantly inhibited PARP1 activity with an IC50 value of 82 ± 9 nM. The current study aimed to explore the mechanism(s) underlying the antitumor activity of 4F-DDC under in vivo and in vitro conditions. 4F-DDC was found to selectively inhibit the proliferation of BRCA mutant cells, with highly potent effects on HCC-1937 (BRCA1-/-) cells. Furthermore, 4F-DDC was found to induce apoptosis and G2/M cell cycle arrest in HCC-1937 cells. Interestingly, immunofluorescence and Western blot results showed that 4F-DDC induced DNA double strand breaks and further activated the cGAS-STING pathway in HCC-1937 cells. In vivo analysis results revealed that 4F-DDC inhibited the growth of HCC-1937-derived tumor xenografts, possibly via the induction of DNA damage and activation of the cGAS-STING pathway. In summary, the current study provides a new perspective on the antitumor mechanism of PARP inhibitors and showcases the therapeutic potential of 4F-DDC in the treatment of breast cancer.

Excavatolide C/cisplatin combination induces antiproliferation and drives apoptosis and DNA damage in bladder cancer cells.

Excavatolide C (EXCC), a marine coral-derived compound, exhibits an antiproliferation effect on bladder cancer cells. The present study evaluated the improvement in the antiproliferation ability of EXCC by co-treatment with cisplatin in bladder cancer cells. EXCC/cisplatin (12.5 and 1 µg/mL) showed higher antiproliferation effects on bladder cancer cells than single treatments (EXCC or cisplatin alone) in the 48 h ATP assay. EXCC/cisplatin also enhanced the increase in subG1, annexin V-mediated apoptosis, and activation of poly (ADP-ribose) polymerase (PARP) and several caspases (caspases 3, 8, and 9) compared to the single treatments. Cellular and mitochondrial oxidative stress was enhanced with EXCC/cisplatin compared to the single treatments according to analyses of reactive oxygen species (ROS), mitochondrial superoxide, and mitochondrial membrane potential; in addition, cellular antioxidants, such as glutathione (GSH), and the mRNA expressions of antioxidant signaling genes (catalase and NFE2-like bZIP transcription factor 2) were downregulated. EXCC/cisplatin treatment produced more DNA damage than the single treatments, as indicated by γH2AX and 8-hydroxy-2'-deoxyguanosine levels. Moreover, several DNA repair genes for homologous recombination (HR) and non-homologous end joining (NHEJ) were downregulated in EXCC/cisplatin compared to others. The addition of the GSH precursor N-acetylcysteine, which has ROS scavenging activity, attenuated all EXCC/cisplatin-induced changes. Notably, EXCC/cisplatin showed lower antiproliferation, apoptosis, ROS induction, GSH depletion, and γH2AX DNA damage in normal cells than in bladder cancer cells. Therefore, the co-treatment of EXCC/cisplatin reduces the proliferation of bladder cancer cells via oxidative stress-mediated mechanisms with normal cell safety.

Harnessing the effects of hypoxia-like inhibition on homology-directed DNA repair.

Hypoxia is a hallmark feature of the tumor microenvironment which can promote mutagenesis and instability. This increase in mutational burden occurs as a result of the downregulation of DNA repair systems. Deficits in the DNA damage response can be exploited to induce cytotoxicity and treat advanced stage cancers. With the advent of precision medicine, agents such as Poly (ADP-ribose) polymerase (PARP) inhibitors have been used to achieve synthetic lethality in homology directed repair (HDR) deficient cancers. However, most cancers lack these predictive biomarkers. Treatment for the HDR proficient population represents an important unmet clinical need. There has been interest in the use of anti-angiogenic agents to promote tumor hypoxia and induce deficiency in a HDR proficient background. For example, the use of cediranib to inhibit PDGFR and downregulate enzymes of the HDR pathway can be used synergistically with a PARP inhibitor. This combination can improve therapeutic responses in HDR proficient cancers. Preclinical results and Phase II and III clinical trial data support the mechanistic rationale for the efficacy of these agents in combination. Future investigations should explore the effectiveness of cediranib and other anti-angiogenic agents with a PARP inhibitor to elicit an antitumor response and sensitize cancers to immunotherapy.

Is Parthanatos Involved in Varicocele?

Varicoceles (VCs) have received widespread attention as a primary factor affecting male fertility and a pathological condition that may lead to decreased sperm count and motility in patients. Many studies have shown that an imbalance of local antioxidant balance exists in patients with VC, leading to an obvious increase in the content of reactive oxygen species (ROS) and may cause reductive stress. Excessive ROS may aggravate spermatogenesis dysfunction and affect male fertility. Poly(ADP-ribose) polymerase (PARP) is an enzyme associated with DNA repair in eukaryotic cells, can be activated by DNA fragments with structural damage, and has been considered a DNA damage receptor in DNA damage repair and apoptosis. We built a rat model of VC and an oxidative damage model of a spermatocyte-derived cell line (GC-2 cells) induced by hydrogen peroxide to study the role of PARP1 in VC. Differentially expressed genes (DEGs) were obtained by RNA sequencing in the testes of VC rats. Analysis of DEGs revealed some genes with significantly altered expression, which were validated in rat and cell models. Immunofluorescence, real-time quantitative PCR analysis, Western blot, and flow cytometry were used to analyze the changes between the control group and the VC or hydrogen peroxide group. Overall, we found that PARP1 protein expression increased in VC rats and in the hydrogen peroxide-induced oxidative stress model of GC-2 cells. Parthanatos may be one of the factors leading to reduced reproductive capacity in VC patients. Our study provides novel insights into the mechanisms of male infertility induced by oxidative stress and provides a new therapeutic target for VC.

Serine metabolism remodeling after platinum-based chemotherapy identifies vulnerabilities in a subgroup of resistant ovarian cancers.

Resistance to platinum-based chemotherapy represents a major clinical challenge for many tumors, including epithelial ovarian cancer. Patients often experience several response-relapse events, until tumors become resistant and life expectancy drops to 12-15 months. Despite improved knowledge of the molecular determinants of platinum resistance, the lack of clinical applicability limits exploitation of many potential targets, leaving patients with limited options. Serine biosynthesis has been linked to cancer growth and poor prognosis in various cancer types, however its role in platinum-resistant ovarian cancer is not known. Here, we show that a subgroup of resistant tumors decreases phosphoglycerate dehydrogenase (PHGDH) expression at relapse after platinum-based chemotherapy. Mechanistically, we observe that this phenomenon is accompanied by a specific oxidized nicotinamide adenine dinucleotide (NAD+) regenerating phenotype, which helps tumor cells in sustaining Poly (ADP-ribose) polymerase (PARP) activity under platinum treatment. Our findings reveal metabolic vulnerabilities with clinical implications for a subset of platinum resistant ovarian cancers.

Aluminium exposure leads to neurodegeneration and alters the expression of marker genes involved to parkinsonism in zebrafish brain.

Aluminium, despite being extremely widespread in the world, is a non-essential metal to human metabolism. This metal is known to have toxic effects on a variety of organs including the brain and is considered an etiological factor in neurodegenerative diseases. However, the molecular mechanisms by which aluminium exerts neurotoxic effects are not yet completely understood. Zebrafish is an animal model also used to study neurodegenerative diseases since the overall anatomical organization of the central nervous system is relatively conserved and similar to mammals. Adult zebrafish were exposed to 11 mg/L of Al for 10, 15, and 20 days and the neurotoxic effects of aluminium were analysed by histological, biochemical, and molecular evaluations. Histological stainings allowed to evaluation of the morphology of the brain parenchyma, the alteration of myelin and the activation of neurodegenerative processes. The expression of the Glial Fibrillary Acidic Protein, a marker of glial cells, was evaluated to observe the quantitative alteration of this important protein for the nervous system. In addition, the poly(ADP-ribose) polymerase activity was measured to verify a possible oxidative DNA damage caused by exposure to this metal. Finally, the evaluation of the markers involved in Parkinsonism was assessed by Real-Time PCR to better understand the role of aluminium in the regulation of genes related to Parkinson's neurodegenerative disease. Data showed that aluminium significantly affected the histology of cerebral tissue especially in the first periods of exposure, 10 and 15 days. This trend was also followed by the expression of GFAP. At longer exposure times, there was an improvement/stabilization of the overall neurological conditions and decrease in PARP activity. In addition, aluminium is involved in the deregulation of the expression of genes closely related to Parkinsonism. Overall, the data confirm the neurotoxicity induced by aluminium and shed a light on its involvement in neurodegenerative processes.

Effect of Genetic Polymorphism Including NUP153 and SVEP1 on the Pharmacokinetics and Pharmacodynamics of Ticagrelor in Healthy Chinese Subjects.

BACKGROUND AND OBJECTIVE: The search for potential gene loci that affect the pharmacodynamics and pharmacokinetics of ticagrelor is a matter of broad clinical interest. The objective of this study was to investigate the effect of genetic polymorphisms on the pharmacokinetics and pharmacodynamics of ticagrelor in healthy Chinese subjects. METHODS: This is a multi-center study in China, including three hospitals from Beijing, Nanchang, and Changsha. Healthy Chinese subjects aged 18-45 years with unknown genotypes were included. All subjects received a single oral dose of 90 mg of ticagrelor. Platelet aggregation and the area under the concentration-time curve for ticagrelor and its major active metabolite in plasma samples were assessed. Genome-wide association studies and candidate gene association analysis related to ticagrelor were performed. RESULTS: One hundred and seventy-five native Chinese subjects were enrolled and completed the study. According to the p value, the threshold of ticagrelor population was 6.57 × 10-7 (0.05/76106), one single-nucleotide polymorphism chr6:17616513 of gene NUP153 (p = 2.03 × 10-7) related to the area under the concentration-time curve for plasma concentration at time zero versus the last measurable timepoint, and one single nucleotide polymorphism rs17204533 of gene SVEP1 (p = 3.96 × 10-7) related to P2Y12 reaction unit12h of ticagrelor was identified. In addition, L1TD1, CETP, CLEC2A, CHSY1, PDZRN3, CTU2, PIEZO1, APOBEC1, SEMA6A, KAZN, and FASN polymorphisms might influence the pharmacokinetics of ticagrelor, while PARP10, TRIB1, CYP2C19, and UGT2B7 might affected its pharmacodynamics. CONCLUSIONS: Genetic variation affects the pharmacokinetics and pharmacodynamics of ticagrelor in healthy individuals. The detection of NUP153, SVEP1 gene variation will be helpful for pharmacodynamic prediction and evaluation, and the regulation of these genes may be the target of new drug development. Further studies are required to confirm the results and explore whether these single-nucleotide polymorphisms are associated only with platelet activity or also with cardiovascular events and all-cause mortality. CLINICAL TRIAL REGISTRATION: NCT03161002.

Physalin B inhibits cell proliferation and induces apoptosis in undifferentiated human gastric cancer HGC-27 cells.

BACKGROUND: Physalin B (PB) from Physalis angulata L. (Solanaceae) is a naturally occurring secosteroid with multiple biological activities, including anti-inflammatory and anticancer activity. However, PB's effects and mechanisms in human gastric cancer (GC) cells are not well characterized. METHODS: The undifferentiated GC cell line HGC-27 and semi-differentiated GC cell line SGC-7901 were treated with PB. Cell counting kit-8 (CCK-8) and colony formation assays were performed to evaluate cell viability. Apoptosis and the cell cycle were assessed by Annexin V/PI and PI/RNase DNA staining assays, respectively, and Western blotting was used to evaluate the expression of a protein. RESULTS: PB significantly inhibited the proliferation of HGC-27 cells in a dose- and time-dependent manner. Moreover, PB induced G0/G1 cycle arrest and caspase-dependent apoptosis of HGC-27 cells. Cleaved caspases 8, 3, and 7, poly(ADP)-ribose polymerase (PARP), and the cyclin-dependent kinase (CDK) inhibitor p-Chk2 was induced by PB in HGC-27 cells, while the cell cycle-related proteins cyclin D1, cyclin D3, CDK4, CDK6, cyclin E, and phosphorylated retinoblastoma tumor suppressor protein (p-Rb) were downregulated in a dose-dependent manner. CONCLUSIONS: PB inhibits proliferation via cyclin-dependent kinase and induces caspase-dependent apoptosis in HGC-27 cells, suggesting that PB might be a novel and effective agent for undifferentiated GC therapy.

Emerging roles of eraser enzymes in the dynamic control of protein ADP-ribosylation.

Protein ADP-ribosylation is essential for the regulation of several cellular pathways, enabling dynamic responses to diverse pathophysiological conditions. It is modulated through a dynamic interplay between ADP-ribose readers, writers and erasers. While ADP-ribose synthesis has been studied and reviewed extensively, ADP-ribose processing by erasing enzymes has received comparably less attention. However, major progress in the mass spectrometric identification of ADP-ribosylated residues and the biochemical characterization of ADP-ribose erasers has substantially expanded our knowledge of ADP-ribosylation dynamics. Herein, we describe recent insights into the biology of ADP-ribose erasers and discuss the intricately orchestrated cellular processes to switch off ADP-ribose-dependent mechanisms.

A New DNA Break Repair Pathway Involving PARP3 and Base Excision Repair Proteins.

Poly(ADP-ribosyl)ation, which is catalyzed by PARP family proteins, is one of the main reactions in the cell response to genomic DNA damage. Massive impact of DNA-damaging agents (such as oxidative stress and ionizing radiation) causes numerous breaks in DNA. In this case, the development of a fast cell response, which allows the genomic DNA integrity to be retained, may be more important than the repair by more accurate but long-term restoration of the DNA structure. This is the first study to show the possibility of eliminating DNA breaks through their PARP3-dependent mono(ADP-ribosyl)ation followed by ligation and repair of the formed ribo-AP sites by the base excision repair (BER) enzyme complex. Taken together, the results of the studies on ADP-ribosylation of DNA and the data obtained in this study suggest that PARP3 may be a component of the DNA break repair system involving the BER enzyme complex.

Reactive oxygen species-induced parthanatos of immunocytes by human cytomegalovirus-associated substance.

Previous studies have examined various immune evasion strategies of human cytomegalovirus (HCMV) to gain understanding of its pathogenesis. Although the mechanism that underlies immunocyte destruction near HCMV-infected lesions has yet to be established, it is here shown that substances produced by HCMV-infected cells induce death in several types of immunocytes, but not in fibroblasts or astrocytomas. These substances contain HCMV proteins and were termed HCMV-associated insoluble substance (HCMVAIS). The mechanism by which HCMVAIS induces cell death was characterized to improve understanding the death of immunocytes near HCMV-infected lesions. HCMVAIS were found to trigger production of intracellular nicotinamide adenine dinucleotide phosphate oxidase-derived reactive oxygen species (ROS), resulting in cell death, this effect being reversed following treatment with ROS inhibitors. Cell death was not induced in splenocytes from NOX-2 knockout mice. It was hypothesized that DNA damage induced by oxidative stress initiates poly ADP-ribose polymerase-1 (PARP-1)-mediated cell death, or parthanatos. HCMVAIS-induced cell death is accompanied by PARP-1 activation in a caspase-independent manner, nuclear translocation of apoptosis-inducing factor (AIF), and DNA fragmentation, which are typical features of parthanatos. Treatment with an AIF inhibitor decreased the rate of HCMVAIS-induced cell death, this being confirmed by hematoxylin and eosin staining; cell death in most HCMV-positive foci in serial section samples of a large intestine with HCMV infection was TUNEL-positive, cleaved caspase 3-negative and CD45-positive. Taken together, these data suggest that HCMV inhibits local immune responses via direct killing of immunocytes near HCMV-infected cells through ROS-induced parthanatos by HCMVAIS.

DNA polymerase ß-dependent cell survival independent of XRCC1 expression.

Base excision repair (BER) is a primary mechanism for repair of base lesions in DNA such as those formed by exposure to the DNA methylating agent methyl methanesulfonate (MMS). Both DNA polymerase ß (pol ß)- and XRCC1-deficient mouse fibroblasts are hypersensitive to MMS. This is linked to a repair deficiency as measured by accumulation of strand breaks and poly(ADP-ribose) (PAR). The interaction between pol ß and XRCC1 is important for recruitment of pol ß to sites of DNA damage. Endogenous DNA damage can substitute for MMS-induced damage such that BER deficiency as a result of either pol ß- or XRCC1-deletion is associated with sensitivity to PARP inhibitors. Pol ß shRNA was used to knock down pol ß in Xrcc1(+/+) and Xrcc1(-/-) mouse fibroblasts. We determined whether pol ß-mediated cellular resistance to MMS and PARP inhibitors resulted entirely from coordination with XRCC1 within the same BER sub-pathway. We find evidence for pol ß-dependent cell survival independent of XRCC1 expression for both types of agents. The results suggest a role for pol ß-dependent, XRCC1-independent repair. PAR immunofluorescence data are consistent with the hypothesis of a decrease in repair in both pol ß knock down cell variants.

Strategies for targeting the DNA damage response for cancer therapeutics.

The DNA damage response is critical for cells to maintain genome stability and survival. In this review, we discuss approaches to targeting critical elements of the DNA damage response for radiosensitization and chemosensitization. In addition, we also discuss strategies for targeting DNA damage response and DNA repair defects in cancer cells for synthetic lethality.

The interaction between the PARP10 protein and the NS1 protein of H5N1 AIV and its effect on virus replication.

BACKGROUND: During the process that AIV infect hosts, the NS1 protein can act on hosts, change corresponding signal pathways, promote the translation of virus proteins and result in virus replication. RESULTS: In our study, we found that PARP domain and Glu-rich region of PARP10 interacted with NS1, and the presence of NS1 could induce PARP10 migrate from cytoplasm to nucleus. NS1 high expression could reduce the endogenous PARP10 expression. Cell cycle analysis showed that with inhibited PARP10 expression, NS1 could induce cell arrest in G2-M stage, and the percentage of cells in G2-M stage rise from the previous 10%-45%, consistent with the cell proliferation result. Plague forming unit measurement showed that inhibited PARP10 expression could help virus replication. CONCLUSIONS: In a word, our results showed that NS1 acts on host cells and PARP10 plays a regulating role in virus replication.

Multimodality molecular imaging of apoptosis in oncology.

OBJECTIVE: The purposes of this review are to describe the signaling pathways of and the cellular changes that occur with apoptosis and other forms of cell death, summarize tracers and modalities used for imaging of apoptosis, delineate the relation between apoptosis and inhibition of protein translation, and describe spectroscopic technologies that entail high-frequency ultrasound and infrared and midinfrared light in characterizing the intracellular events of apoptosis. CONCLUSION: Apoptosis is a highly orchestrated set of biochemical and morphologic cellular events. These events present many potential targets for the imaging of apoptosis in vivo. Imaging of apoptosis can facilitate early assessment of anticancer treatment before tumor shrinkage, which may increase the effectiveness of delivery of chemotherapy and radiation therapy and speed drug development.

Metformin induces both caspase-dependent and poly(ADP-ribose) polymerase-dependent cell death in breast cancer cells.

There is substantial evidence that metformin, a drug used to treat type 2 diabetics, is potentially useful as a therapeutic agent for cancer. However, a better understanding of the molecular mechanisms through which metformin promotes cell-cycle arrest and cell death of cancer cells is necessary. It will also be important to understand how the response of tumor cells differs from normal cells and why some tumor cells are resistant to the effects of metformin. We have found that exposure to metformin induces cell death in all but one line, MDA-MB-231, in a panel of breast cancer cell lines. MCF10A nontransformed breast epithelial cells were resistant to the cytotoxic effects of metformin, even after extended exposure to the drug. In sensitive lines, cell death was mediated by both apoptosis and a caspase-independent mechanism. The caspase-independent pathway involves activation of poly(ADP-ribose) polymerase (PARP) and correlates with enhanced synthesis of PARP and nuclear translocation of apoptosis-inducing factor (AIF), which plays an important role in mediating cell death. Metformin-induced, PARP-dependent cell death is associated with a striking enlargement of mitochondria. Mitochondrial enlargement was observed in all sensitive breast cancer cell lines but not in nontransformed cells or resistant MDA-MB-231. Mitochondrial enlargement was prevented by inhibiting PARP activity or expression. A caspase inhibitor blocked metformin-induced apoptosis but did not affect PARP-dependent cell death or mitochondrial enlargement. Thus, metformin has cytotoxic effects on breast cancer cells through 2 independent pathways. These findings will be pertinent to efforts directed at using metformin or related compounds for cancer therapy.

Age-related loss of stress-induced nuclear proteasome activation is due to low PARP-1 activity.

Changes in protein turnover are among the dominant metabolic changes during aging. Of special importance is the maintenance of nuclear protein homeostasis to ensure a coordinated cellular metabolism. Therefore, in the nucleus a special PARP-1-mediated mechanism of proteasomal activation exists to ensure a rapid degradation of oxidized nuclear proteins. It was already demonstrated earlier that the cytosolic proteasomal system declines dramatically with aging, whereas the nuclear proteasome remains less affected. We demonstrate here that the stress-mediated proteasomal activation in the nucleus declines during replicative senescence of human fibroblasts. Furthermore, we clearly show that this decline in the PARP-1-mediated proteasomal activation is due to a decline in the expression and activity of PARP-1 in senescent fibroblasts. In a final study we show that this process also happens in vivo, because the protein expression level of PARP-1 is significantly lower in the skin of aged donors compared to that of young ones. Therefore, we conclude that the rate-limiting factor in poly(ADP-ribose)-mediated proteasomal activation in oxidative stress is PARP-1 and not the nuclear proteasome itself.

Pyrrolo[1,2-b][1,2,5]benzothiadiazepines (PBTDs) exert their anti-proliferative activity by interfering with Akt-mTOR signaling and bax:bcl-2 ratio modulation in cells from chronic myeloid leukemic patients.

In our study we found that pyrrolo[1,2-b][1,2,5]benzothiadiazepines (PBTDs) mediated apoptosis in primary leukemia cells from 27 chronic myelogenous leukemia (CML) patients at onset through the activation of the caspase-9 and -3, and cleavage of poly (ADP-ribose) polymerase (PARP). The bax:bcl-2 ratio was increased as a consequence of down-regulation of bcl-2 and up-regulation of bax proteins in response to treatment with PBTDs. In addition, PBTDs were able to induce cell death in primary leukemia cells derived from 23 CML-chemoresistant patients. Furthermore, the effects of PBTDs on the Akt-mTOR (mammalian target of rapamycin) pathway were determined by Western blot. PBTDs possessed inhibitory activity against mTOR and also impeded hyper-phosphorylation of Akt as a feedback of inhibition of mTOR by rapamycin. The results presented in this study demonstrate that we have identified the PBTDs as restoring the apoptotic pathways both in primary leukemia cells derived from CML patients at onset and in primary leukemia cells derived from CML-chemoresistant patients, thus showing their ability to undergo apoptosis. These compounds constitute a promising therapeutic approach for patients with leukemia. They provide the basis for new strategies for an additional anticancer drug in leukemia therapies, especially when conventional ones fail.

Programmed necrosis induced by asbestos in human mesothelial cells causes high-mobility group box 1 protein release and resultant inflammation.

Asbestos carcinogenesis has been linked to the release of cytokines and mutagenic reactive oxygen species (ROS) from inflammatory cells. Asbestos is cytotoxic to human mesothelial cells (HM), which appears counterintuitive for a carcinogen. We show that asbestos-induced HM cell death is a regulated form of necrosis that links to carcinogenesis. Asbestos-exposed HM activate poly(ADP-ribose) polymerase, secrete H(2)O(2), deplete ATP, and translocate high-mobility group box 1 protein (HMGB1) from the nucleus to the cytoplasm, and into the extracellular space. The release of HMGB1 induces macrophages to secrete TNF-alpha, which protects HM from asbestos-induced cell death and triggers a chronic inflammatory response; both favor HM transformation. In both mice and hamsters injected with asbestos, HMGB1 was specifically detected in the nuclei, cytoplasm, and extracellular space of mesothelial and inflammatory cells around asbestos deposits. TNF-alpha was coexpressed in the same areas. HMGB1 levels in asbestos-exposed individuals were significantly higher than in nonexposed controls (P < 0.0001). Our findings identify the release of HMGB1 as a critical initial step in the pathogenesis of asbestos-related disease, and provide mechanistic links between asbestos-induced cell death, chronic inflammation, and carcinogenesis. Chemopreventive approaches aimed at inhibiting the chronic inflammatory response, and especially blocking HMGB1, may decrease the risk of malignant mesothelioma among asbestos-exposed cohorts.

SZ-685C, a marine anthraquinone, is a potent inducer of apoptosis with anticancer activity by suppression of the Akt/FOXO pathway.

BACKGROUND AND PURPOSE: The aims of this study were to investigate the anti-cancer activity of SZ-685C, an anthracycline analogue isolated from marine-derived mangrove endophytic fungi, and to explore the molecular mechanisms underlying such activity. EXPERIMENTAL APPROACH: The effect of SZ-685C on the viability of cancer cell lines was investigated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. SZ-685C-induced apoptosis was assessed by Annexin V-fluorescein isothiocyanate/propidium iodide staining, terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling assay and analysis of caspase activation. The effect of SZ-685C on the Akt/FOXO pathway was studied using Western blotting analysis, and the in vivo anti-tumour efficacy was examined in an MDA-MB-435 breast cancer xenograft model. KEY RESULTS: SZ-685C suppressed the proliferation of six cancer cell lines derived from human breast cancer, prostate cancer, glioma and hepatoma (IC(50) values ranged from 3.0 to 9.6 microM) and the growth of breast cancer xenografts in mice. SZ-685C had a direct apoptosis-inducing effect through both the extrinsic and intrinsic apoptotic pathways, as shown by activation of caspase-8 and 9 as well as effector caspase-3 and poly (ADP-ribose) polymerase. Phosphorylation of Akt and its downstream effectors, forkhead box protein O1 and forkhead box protein O3a, was down-regulated in SZ-685C-treated cancer cells. Furthermore, the pro-apoptotic protein Bim was up-regulated by SZ-685C treatment consistent with FOXO dephosphorylation. CONCLUSIONS AND IMPLICATIONS: SZ-685C could induce apoptosis through the Akt/FOXO pathway, which consequently leads to the observed anti-tumour effect both in vitro and in vivo. Our data suggest that SZ-685C may be a potentially promising Akt inhibitor and anti-cancer drug candidate.